Transcription of Modbus and DNP3 Communication Protocols
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Modbus and dnp3 Communication Protocols Provided by: Triangle MicroWorks, Inc. Raleigh, North Carolina Phone +1 919-870-5101 Fax +1 919-870-6692 Modbus and DNP are both byte-oriented Protocols . Modbus is an application layer protocol, while DNP contains Application and Data Link Layers, with a pseudo-transport layer. Both Protocols are widely used over a variety of physical layers, including RS-232, RS-422, RS-485, and TCP/IP. Modbus has a separate specification for use over TCP/IP ( Modbus -TCP). With DNP, the protocol is simply encapsulated within TCP/IP. History Modbus was developed in the process-control industry by Modicon in 1979. It was originally designed as a simple way to transfer data between controls and sensors via RS-232 interfaces. Modbus now supports other Communication media, including TCP/IP. Modbus is now an open standard, administered by the Modbus -IDA ( ). The Distributed Networking Protocol (DNP) was originally developed by Westronic, Inc.
Reading Data (Inputs) Modbus reads values from ranges of inputs (and/or outputs) by issuing a single request to read each range or type. All data are treated as "present value".
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